Over the past decades, the synthesis of inorganic and organic nanocomposites has received much attention in the range of fields including electroanalysis of organic chemicals. In this regard, we have prepared copper oxide nanoparticle (CuO NPs) decorated graphene/beta-cyclodextrin (GR-beta-CD) composites using a simple electrochemical methodology, where the CuO NPs are electrodeposited on GR-beta-CD composite modified electrodes. A stable GR-beta-CD composite was prepared by sonication of GR in beta-CD aqueous solution. As-prepared GR-beta-CD/CuO NPs composites were characterized by the high-resolution scanning electron microscopy, X-ray diffraction, and Raman spectroscopy. Cyclic voltammetry results reveal that the GR-beta-CD/CuO NPs composite modified electrode exhibits an excellent catalytic activity and lower reduction potential towards the electrochemical detection of metronidazole (MTZ) over other modified electrodes including GR, GR-beta-CD, and CuO NPs. Under optimized conditions, amperometry was used for the determination of MTZ using GR-beta-CID/CuO NPs composite modified electrodes. The response of MTZ using the composite electrodes was linear over the range from 0.002 to 210.0 mu M. This sensor showed the lowest limit of detection of 0.6 nM and was much lower than the previously reported MTZ sensors. In addition, the sensor is highly sensitive, selective and durable in the presence of a range of potentially interfering electroactive compounds. (C) 2018 Elsevier Inc. All rights reserved.